In the packaging arts, it is generally known to provide resealable closures on containers whose contents are not necessarily consumed all at once. They are used for packaging a wide variety of products, and are notably favoured for beverages and other comestibles.
A number of different kinds of resealable closures are known, for instance swinging lever closures, caps, and sliding push-pull closures. Among such closures, caps are regarded as particularly advantageous in that the consumer may open, re-seal, and re-open the container without the need of tools. Of these, the two types which command the overwhelming majority of market share are the press-on snap cap and the screw-on cap.
Snap-caps are generally flat and fabricated from a flexible plastic, and typically comprise an annular groove disposed on a lower surface of the cap; this annular groove clasps a bead disposed about a mouth of the container; when attaching the cap the bead is pressed into the groove, causing the groove to open enough to permit the bead to seat therein.
At this point, the elasticity of the cap causes the groove to close around the seated bead, retaining the cap on the container. To open the container, the cap is merely grasped at one edge and bent upwards; the groove deforms to permit the bead to be extracted from the cap as it is removed from the container.
Such snap-caps are inexpensive to fabricate and require relatively little force to open and close. However, this also means that the strength of the joint between cap and container is weak. As a result, the cap may be easily dislodged when the cap or container are subjected to external shocks and impacts (particularly from the lateral direction) that may be encountered during transport and use of the container, leading to leakage and spills.
Screw-on caps, in contrast, are generally fabricated from a hard plastic or metal, and comprise internal threads which engage complementary threads disposed about the neck of the container. When screwed tightly to the container they provide a tight, leakage-resistant seal, and cannot be dislodged during normal use by external shocks and impacts as snap-caps can.
However, screw-on caps are less than ideal, in that they require a large amount of force to open and close. This poses difficulties to children, the elderly, and others who do not have sufficient strength or manual dexterity to properly tighten and loosen such a closure. Moreover, the provision of threads in the cap and on the neck of the container requires an increased level of precision in the manufacture of both relative to other types of closures, increasing the cost of the container.
There is thus a need for a cap for a container which may be easily opened and closed, which is resilient to shock and impact, and which is inexpensive to fabricate and implement. It is therefore an object of the invention to provide a closure which presents at least some of these attributes.